Liquid epoxy compounds containing an alicyclic skeleton and having satisfactory optical transparency and high heat resistance are frequently used in epoxy resin compositions for sealing optical semiconductor elements. Examples of these epoxy compounds are CELLOXIDE 2021 (3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate), CELLOXIDE 2081 (an adduct between 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate and ε-caprolactone dimer), and CELLOXIDE 3000 (1,2,8,9-diepoxylimonene), each available from Daicel Chemical Industries, Ltd.
Epoxy compounds having a 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate structure typified by CELLXIDE 2021 yield cured products excellent in heat resistance and optical transparency and are used in resins for sealing optical semiconductors such as LED. These cycloaliphatic epoxy compounds such as CELLOXIDE 2021, however, are insufficient in heat-cycle resistance and invite cracking to thereby decrease the reliability of product electronic parts.
Conventional proposals for improving physical properties of epoxy resins, such as for increasing impact resistance and preventing cracking, are as follows. Japanese Unexamined Patent Application Publication (JP-A) No. 09-255764, for example, discloses an epoxy resin composition for sealing optical semiconductors, containing a diglycidyl ether of hydrogenated bisphenol-A. JP-A No. 10-156952 discloses a stereolithographic resin composition using a cycloaliphatic epoxy compound as in the present invention. JP-A No. 2000-63485 discloses a curable composition for buildup, containing a specific cycloaliphatic epoxy compound and a polyepoxy compound having a polyphenol skeleton. JP-A No. 09-71636 discloses an active energy ray-curable composition using a cycloaliphatic epoxy compound as in the present invention.    Patent Document 1: Japanese Unexamined Patent Application Publication (JP-A) No. 09-255764    Patent Document 2: Japanese Unexamined Patent Application Publication (JP-A) No. 10-156952    Patent Document 3: Japanese Unexamined Patent Application Publication (JP-A) No. 2000-63485    Patent Document 4: Japanese Unexamined Patent Application Publication (JP-A) No. 09-71636